1. Field of the Invention
The field of art to which this invention pertains is the separation of fatty acids from unsaponifiables by a process employing liquid-liquid extraction.
2. Background Information
There is a wealth of patent art teaching the separation of unsaponifiables from tall oil soap using liquid-liquid extraction schemes. Examples of such schemes are as disclosed in U.S. Pat. Nos. 2,530,809 to Christenson et al., 2,530,810 to Christenson et al., 2,640,823 to Gloyer et al., 3,453,253 to Brink, 3,803,114 to Mitchell et al., 3,965,085 to Holmbom et al., 4,422,966 to Amer and a publication from the Technical Research Centre of Finland, entitled "Refining of Tall Oil Products by Column Liquid-Liquid Extraction." In these schemes unsaponifiables are extracted from aqueous solution with salts of fatty and rosin acids (soaps) by contacting the solutions with a solvent, such as a hydrocarbon or alcohol, in which the unsaponifiables are soluble and thereby removing the unsaponifiables from the salts. The fatty and rosin acid salts, according to these references, may then be converted to the acid forms to obtain tall oil.
With further regard to the above mentioned Mitchell et al. patent, it is taught (column 4) that emulsions formed when the attempt is made to extract unsaponifiables from aqueous solutions with a hydrocarbon solvent cause a serious problem which prevents successful completion of the extraction. This "problem" was solved by the use of certain alcohols which acted as de-emulsifiers. The teaching goes on to state that if water, soap skimmings, alcohol and hydrocarbon were shaken up together, the unsaponifiables would be extracted by the hydrocarbon and, when the mixture was allowed to stand, the components would quickly separate into a lower phase, consisting mainly of soap-water alcohol, and an upper phase consisting mainly of hydrocarbon and unsaponifiables.
My copending application Ser. No. 598,121, now U.S. Pat. No. 4,495,094, teaches the separation of fatty and rosin acids (not salts) from unsaponifiables by a liquid-liquid extraction technique. I have also discovered that mixtures comprised of unsaponifiables and fatty acids may be separated by the same liquid extraction technique.